Certain ceramics, such as Silicon carbide (SiC) Boron Nitride (BN) and Aluminum Nitride (AlN), are known to exhibit electrical properties ranging from insulating to semiconducting to conducting, as discussed in U.S. Pat. No. 5,145,741, issued Sep. 8, 1992, entitled "Converting Ceramic Materials to Electrical Conductors and Semiconductors", and U.S. Pat. No. 5,391,841, issued Feb. 21, 1995, entitled "Laser Processed Coatings on Electronic Circuit Substrates", both issued to Nathaniel R. Quick. The ceramics under consideration herein, are used to create devices such as conductive tabs, interconnects, vias, wiring patterns, resistors, capacitors, semiconductor devices and the like electronic components by laser synthesis on the surfaces and within the body of such ceramics to thereby eliminate photolithography processes which require numerous steps and generate undesirable chemical pollutants when processing such traditional electronic devices, components and circuitry.
As is well known Alumina (Al.sub.2 O.sub.3) dominates the dielectric market as an integrating substrate or device carrier in electronics packaging. AlN, BN and SiC are also of interest, due to their Thermal Coefficient of Expansion (TCE) and for their dielectric constant and higher thermal conductivity than that of Al.sub.2 O.sub.3. These properties are of substantial interest for new high temperature and aggressive environment applications, particularly where high integrated circuit packing densities are required. In the prior art, metallization methods, including dry-film imaging and screen printing have been used for the production of conductive patterns on Alumina, however, metal compatibility with the newer high thermal conductivity ceramic materials such as AlN, BN and SiC, have not been completely solved. Copper and silver paste exhibit a TCE mismatch aggravated by high temperatures and are subject to oxidation which increases their resistivity. In particular, bonding of copper to AlN has proved to be nontrivial. Alumina or stoichiometric aluminum oxynitride (AlON) coatings must be developed on the AlN surface through passivation processes. These passivation processes have poor reproducibility, especially when hot pressed AlN substrates are used. Thus, the direct laser synthesis of conductors in AlN, BN and SiC substrates appears to provide solutions to this long standing prior art problem with regard to metallization and for more simple processing techniques for creating devices and circuitry that are compatible with selected ceramic substrates, while satisfying the need for higher temperature, aggressive environment, and higher density integrated circuit packaging applications.